There are primarily two types of spondylolysthesis. The first is called isthmic spondylolysthesis, and the second is called degenerative spondylolysthesis. Both result in slippage of one vertebral body forward on another vertebral body. This either results in back pain, and or leg pain. The leg pain occurs as a result of pinching of one of the spinal nerves and is a primary reason to have surgery in this condition.
Isthmic spondylolysthesis is the result of a stress fracture of the spine that usually occurs during childhood. As you age there is an increased sheer stress placed on the intervertebral disc, Because the normal part of the spine called the pars interarticularis is broken, the vertebra moves forward resulting in narrowing of the nerve opening and pinching of the spinal nerve. Degenerative spondylolysthesis rarely begins before the age of 40, and is caused by disc degeneration in conjunction with sagitally oriented facet joints. Here the vertebra moves forward and pinches the spinal nerve.
Before considering surgery a trial of conservative therapy is indicated depending on the severity of the condition. If the condition has started within three months, consider a trial of strengthening exercises, a spinal brace or perhaps a nerve block or an epidural injection. If the injection works for a short time reinjection can sometimes be helpful, however, continued injection can result in permanent nerve damage, and rarely accomplishes anything. If you have severe symptoms for more than a year you should not expect that therapy, exercise or injections will cure you. Both conditions usually require surgery if the symptoms are severe, resulting in loss of function. If the symptoms are mild surgery is not needed. If you are unable to stand for 30 minutes, Walk for more than 2 blocks, have weakness or severe numbness in your legs; you most likely will need surgery. You should have both decompression, which usually means a laminotomy or laminectomy, to take the pressure off of the nerve, combined with a fusion to prevent further slippage of the vertebra.
It is Dr. Light's personal opinion, that spinal reduction or replacement of the proper position of the vertebra gives superior results. This however is not always possible, and can result in injury to the spinal nerves.
If the surgery is performed properly you should have a good result. You can expect substantial reduction in your leg symptoms, and your back pain. Mild pain and stiffness may continue even after surgery. You have a good chance to improve your function. Remember that no matter how optimistic is your surgeon, he cannot make a new nerve or a new disc and some residual symptoms are usually present.